JPH08125000A - Wafer chuck - Google Patents

Abstract

PURPOSE: To maintain and hold the flatness of a surface accurately even when a foreign matter adheres on the rear of a wafer obstructing flatness or the wafer is warped in a wafer chuck holding the wafer. CONSTITUTION: A holding area, in which a wafer 15 is sucked and held, is detained in a narrow region in the outer peripheral section of the wafer 15 and the mixing of a foreign matter is prevented, a variable leakage valve 4 adjusting the pressure of a space section 3b, a vacuum pump 6 and a changeover valve 7 conducting a changeover to high-pressure air are mounted for flattening the warped wafer 15, and proper positive pressure or negative pressure is applied to the wafer in response to the warpage measured value of a laser length measuring instrument 1, thus correcting warpage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer chuck for holding a wafer in a wafer inspection apparatus for inspecting the surface condition of a semiconductor wafer (hereinafter simply referred to as a wafer) and a reduction projection type exposure apparatus for transferring a pattern onto the wafer. .

[0002]

2. Description of the Related Art Usually, for example, a reduction projection type exposure apparatus is
The mask irradiates the light emitted from the light source through the reticle onto the wafer precisely to transfer the pattern. However, a very fine pattern is out of focus even if the focus is slightly defocused, and the accurate pattern cannot be transferred. Therefore, holding the wafer with good flatness has become a serious problem, and various improvements have been made to the wafer chuck that holds the wafer.

FIGS. 2A and 2B are a plan view and a side view of a conventional wafer chuck showing an example. Conventionally, this type of wafer chuck has, for example, as shown in FIG. 2, a concentric convex portion 12 on which a wafer 15 is mounted.
a, 12b, 12c and the convex portions 12a, 12b, 12c
And a vacuum pump 13 that evacuates the space including the groove and the back surface of the wafer 15. In addition, exhaust holes 14a, 14 are provided at the bottom of the groove portion so that air can be exhausted from the space.
b, 14c and 14d are opened, and the respective exhaust holes 14a, 14b, 14c and 14d are connected to the vacuum pump 13
It is designed to communicate with the exhaust pipe of.

In this wafer chuck, even if the wafer 15 is warped through various processes such as an etching process and a film forming process, the convex portion 12 is generated by the suction force of the vacuum pump 13.
It was characterized in that it could be pressed against a, 12b and 12c to correct the warpage and hold it.

[0005]

In the above-mentioned conventional wafer chuck, the wafer is held in close contact with the convex portion during vacuum suction, but when foreign matter is attached to the back surface of the wafer, it is necessary to ensure complete contact. Rather, the part of the wafer sandwiching the foreign matter is raised. as a result,
Since the reduction projection type exposure apparatus repeatedly performs exposure while focusing on the surface of the wafer, there is a problem that defocusing occurs if there is a raised portion. Further, when the central portion of the wafer is recessed downward, a leak occurs between the wafer and the convex portion during vacuum evacuation, which makes it difficult to adsorb the wafer and often cannot hold it.

Therefore, an object of the present invention is to provide a wafer capable of accurately maintaining the surface flatness and holding the wafer even if foreign matter adheres to the back surface of the wafer which obstructs the flatness or the wafer is warped. It is to provide a chuck.

[0007]

A feature of the present invention is that it has a convex portion in which a groove for vacuum adsorption is formed by placing an outer peripheral edge portion of a back surface of a semiconductor wafer with one main surface facing upward, and the convex portion. A cup-shaped supporter that forms a space formed by the recess on the inside and the back surface of the semiconductor wafer, a vacuum pump that evacuates the space and the space of the groove of the support, and the space. A switching valve that is provided in the middle of the path of the pipe that communicates with the exhaust hole of the section and that switches to either the suction port side pipe of the vacuum pump or the high pressure air source supply port side pipe,
A laser length measuring device for irradiating a laser on the central portion of one main surface of the semiconductor wafer to measure the degree of deformation due to the pressure in the space, and a pressure for adjusting the pressure in the space based on the measurement value of the laser length measuring device. 3 is a wafer chuck including a regulator.

[0008]

Next, the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are a plan view and a partially cutaway side view of a wafer chuck showing an embodiment of the present invention. As shown in the figure, this wafer chuck has a convex portion 3a on which an outer peripheral edge portion of the back surface of the wafer 15 is placed and in which a groove 10 for vacuum suction is formed, and the convex portion 3a.
a support 3 in the form of a cup that forms a space 3b formed by the recess inside a and the back surface of the wafer 15, and this support 3
The vacuum pump 6 which evacuates the space portion of the groove 10 through the exhaust passage hole 10a and evacuates the space portion 3b from the exhaust hole 9 and the vacuum pump which is provided in the middle of the passage of the pipe communicating with the exhaust hole 9 of the space portion 3b. 6, a three-way switching valve 7 for switching between the suction port side pipe of 6 and the supply port side pipe of the high-pressure air source, and the pressure of the space 3b by irradiating the central portion of one main surface of the wafer 15 with laser. The laser length measuring device 1 for measuring the degree of deformation by the variable length measuring device, and the measured value of the laser length measuring device 1 is input to the control unit 2 and a signal from the control unit 2 is transferred to the Hals motor 5 to adjust the pressure in the space 3b. A leak valve 4 is provided.

Further, the exhaust suction port of the vacuum pump 6 is branched into two, and one exhaust suction port is connected to the exhaust passage hole 10a communicating with the groove 10 which is the suction hole through the opening / closing valve 7a,
The other exhaust suction port is connected to the exhaust hole 9 communicating with the space 3b via the switching valve 7 and the variable leak valve 4. Further, these pipes are provided with leak valves 8a and 8b for returning the inside of the pipes to the atmosphere in order to release the holding of the wafer 15.

The laser length measuring device 1 is a phase modulation type laser length measuring device and is usually commercially available. This laser length measuring device 1
A laser beam emitted from a laser oscillator is separated into a reference beam and a measurement beam by a deflecting beam splitter, the reference beam is irradiated onto the reference plane of the reference beam and the measuring beam at the central portion of the wafer 15, and the reflected beam is returned to the deflecting beam splitter. The degree of swelling and the degree of swelling of the central portion of the wafer 15 are measured by making the light incident and detecting the phase difference between the two lights. Further, as is well known, the measurement resolution of the laser length measuring device 1 can be up to 1/4 of the wavelength of the laser beam, and is most suitable for wafer flatness measurement which requires non-contact measurement accuracy of 1 μm or less. ing.

The control unit 2 controls the operation of the open / close valve 7a, the operation of the leak valves 8a and 8b, the switching operation of the switching valve 7 and the rotation control of the pulse motor 5 for adjusting the opening degree of the variable leak valve 4. Is. That is, when the wafer 15 that is not vacuum-adsorbed is dented, the switching valve 7 is switched to the piping of the high-pressure air supply port, and conversely, when it is expanded, it is switched to the piping of the suction port side of the vacuum pump 6. Also,
A digital signal indicating a measured value is input from the laser length measuring device 1, an output signal of the number of pulses is sent to the pulse motor 5 according to the number of digital pulses, the leak amount of the variable leak valve 4 is adjusted, and the space 3b of the support base 3 is adjusted. Adjusting pressure.

Next, the operation of this wafer chuck will be described. First, the wafer 15 is placed on the support base 3. Next, the laser length measuring device 1 determines from the measured value whether the wafer 15 is dented or swollen. Here, assuming that the switching valve 7 is inflated, the switching valve 7 is connected to a pipe communicating with the intake port of the vacuum pump 6 and the exhaust hole 9. Next, the vacuum pump 6 is operated to open the opening / closing valve 7a, and the space of the groove 10 and the space 3b are evacuated. This makes wafer 1
5 is attracted to the convex portion 3 a of the support base 3 and the space portion 3
The pressure of b is reduced and the bulge of the central portion of the wafer 15 starts to disappear.

When the bulge disappears and the central portion of the wafer 15 becomes flat and starts to be recessed, the control unit 2 sends a signal of a required pulse number to the pulse motor 5 according to the measurement signal of the laser length measuring device 1 and the variable leak valve. The exhaust capacity of the vacuum pump 6 is reduced by adjusting the opening degree of 7. As a result, the pressure in the space partly rises, and the depression of the wafer 15 is eliminated and the wafer 15 becomes flat. Then, the head of the laser length-measuring device 1 moves to start exposure and start inspection. When the inspection or exposure is completed, the leak valves 8a and 8b are opened, the space 3b and the space of the groove 10 are returned to the atmosphere, and the wafer 15 is removed.

On the contrary, when the wafer 15 is dented, the switching valve 7 is connected to the pipe on the high pressure air side and the pipe communicating with the exhaust hole 9 to hold the outer peripheral edge of the wafer 15 by the suction force of the vacuum pump 6. On the other hand, the pressure in the space 3b is adjusted by the variable leak valve 4 so that the central portion of the wafer 15 is inflated to be flat.

[0016]

As described above, according to the present invention, the area for attracting and holding a wafer is kept to a small area at the outer peripheral edge of the wafer, and the laser length measuring device for measuring the unevenness of the central portion of the wafer and the laser measuring device. By providing a pressure adjusting means for flattening a warped wafer according to the measurement value of the length device, even if the foreign matter adheres to the wafer or the wafer warps, the foreign matter remains between the wafer and the holding unit. There is an effect that the warp can be corrected and the flatness can be obtained and held without intervening.

[Brief description of drawings]

FIG. 1 is a plan view and a partially cutaway side view of a wafer chuck showing an embodiment of the present invention.

FIG. 2 is a plan view and a side view of a conventional wafer chuck.

[Explanation of symbols]

 1 Laser length measuring device 2 Control part 3,11 Support stand 3a, 12a, 12b, 12c Convex part 3b Space part 4 Variable leak valve 5 Pulse motor 6,13 Vacuum pump 7 Switching valve 7a Open / close valve 8a, 8b Leak valve 9, 14a, 14b, 14c, 14d exhaust hole 10 groove 10a exhaust path hole 15 wafer

Claims (1)

[Claims] 1. A semiconductor wafer having a convex portion on which an outer peripheral edge portion of a back surface of a semiconductor wafer is placed with one main surface facing upward and a groove for vacuum suction is formed, and a depression inside the convex portion and the semiconductor wafer. A cup-shaped support base that forms a space portion consisting of the back surface, a vacuum pump that evacuates the space portion of the groove and the space portion of the support base, and a path of a pipe that communicates with an exhaust hole of the space portion. A switching valve provided in the suction port side of the vacuum pump and a piping side of the supply port of the high pressure air source, and a space for irradiating a laser on the central portion of one main surface of the semiconductor wafer. A wafer chuck, comprising: a laser length measuring device for measuring a degree of deformation due to pressure; and a pressure adjusting device for adjusting a pressure in the space portion based on a measurement value of the laser length measuring device.